Construction of pipes

ABSTRACT

An elongate hollow structure and method of constructing the hollow structure is described, the hollow structure including a radially inner portion and a radially outer portion merging together to form a tubular wall structure. The method includes providing the radially inner portion, assembling the radially outer portion about the radially inner portion, and radially expanding the inner portion. The outer portion comprises an outer layer of fibre reinforced composite construction surrounded by a flexible outer casing. A space is provided between the radially inner portion and flexible outer casing. The outer layer includes reinforcement and a binder. The flexible outer casing resists radial expansion of the reinforcement, subjecting it to radial compression. The radially expanding inner portion cooperates with the flexible outer casing to cause the volume of the space to progressively decrease, causing the binder to spread through the space between the radially inner portion and flexible outer casing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §365(b) ofPCT/AU2011/001401 to Neil Deryck Bray Graham, filed Oct. 31, 2011 andentitled “CONSTRUCTION OF PIPES”, the entire contents of which is herebyincorporated by reference herein.

BACKGROUND

1. Field.

The example embodiments generally relate to elongate hollow structuresof composite construction, including in particular tubular structures.

While the example embodiments have been devised particularly in relationto the construction of tubular structures in the form of pipes, it mayalso be applicable to the construction of other elongate hollow elementsincluding tubular elements such as ducts and tubes, tubular structuralelements such as shafts, beams and columns, and other tubular elementsof composite construction.

2. Related Art

The following discussion of the background art is intended to facilitatean understanding of the example embodiments of the present inventiononly. The discussion is not an acknowledgement or admission that any ofthe material referred to is or was part of the common general knowledgeas at the priority date of the application.

It is known to construct pipes using fibre-reinforced plasticcomposites. Typically, such pipes are constructed by a process in whichrovings of filaments of fibre material, (such as glass fibres) areimpregnated with a thermosettable resin or thermoplastic composition andwound back and forth on a mandrel to form a pipe wall structure ofcomposite construction.

Further, there have been attempts to produce a continuous pipe bypultrusion involving a wet body of reinforcement fibres being drawnthrough a heated mould to cure the pipe and the pipe then wound onto aspool. Pipes constructed in this way are typically limited to lengths ofabout 1 km and diameters of about 100 mm

Typically, such pipes are required to bear both hoop and axial stresses,and the construction can be a compromise between the hoop and axialstress bearing properties required for the pipe. Hoop strength can beoptimised by winding the reinforcing filaments at an angle approaching90° to the pipe axis. Axial strength can be optimised by winding thereinforcing filaments at an angle approaching the pipe axis.

The length of pipe that can be constructed in such a way is dictated bythe length of the mandrel or the roll of pipe that can be transported.Consequently, the construction process is not conducive to constructionof long pipes to form a transportation network for liquids and gasses;that is, pipes which are much longer than available mandrels and alsopipes which are of a length to constitute a pipeline extendingcontinuously between two distant locations, perhaps hundreds tothousands of kilometers apart.

It would be advantageous for there to be a way in which a pipeline couldbe constructed using a pipe constructed on a continuous basis; that is,without having to be composed of a series of pipe sections joined one toanother at junctions which are likely constituted areas of weakness instructural integrity of the pipeline

It is against this background, and the problems and difficultiesassociated therewith, that the example embodiments of the presentinvention have been developed.

SUMMARY

An example embodiment of the present invention is directed to a methodof constructing an elongate hollow structure, the elongate hollowstructure having a radially inner portion and a radially outer portion,with the two portions merging together to provide an integrated tubularwall structure, the method comprising: providing the radially innerportion: assembling the radially outer portion about the radially innerportion; and expanding the inner portion; wherein the outer portioncomprises an outer tube of fibre reinforced composite constructionsurrounded by a flexible outer casing. There is a space between theradially inner portion and the flexible outer casing. The outer layer offibre reinforced composite construction comprises reinforcement and abinder. The flexible outer casing serves to resist radial expansion ofthe reinforcement, thereby causing it to be subjected to radialcompression, and the radially expanding inner portion operates inconjunction with the flexible outer casing to cause the volume of thespace between the radially inner portion and the flexible outer casingto progressively decrease, thereby causing the binder within thereinforcement to spread through the space between the radially innerportion and the flexible outer casing.

The reinforcement may comprise one or more layers of reinforcing fabric.In an example, each layer is configured as a tubular layer disposedabout the radially inner portion. Typically, there is a plurality oftubular layers disposed one about another and hence also disposed aboutthe inner portion.

The reinforcing fabric may comprise reinforcing fabric whichincorporates reinforcement fibres featuring quadraxial fibreorientations. The reinforcement fibres may comprise glass fibres. Thequadraxial fibre orientations offer the necessary hoop and axial stressbearing properties to the tubular structure.

In an example, the binder comprises a settable plastic such as aresinous binder, which is commonly referred to as a resin. The bindersets to a resin matrix for binding the layers of reinforcing fabrictogether and to bind the reinforcement to the inner portion to providethe integrated tubular wall structure. The resin matrix may also bindthe reinforcement to the outer casing.

In an example, the inner portion comprises an inner tube comprising aninner liner with a fibrous layer bonded onto one face thereof, whereinthe resinous binder impregnating the reinforcing fabric also impregnatesthe fibrous layer to integrate the outer portion with the inner portion.

In an example, the outer casing comprises an outer layer and a fibrouslayer bonded onto one face thereof, the arrangement being that thefibrous layer confronts the reinforcement. With this arrangement thefibrous layer of the outer casing may provide a breather layer throughwhich air can move.

In an example, the flexible outer casing serves to resist radialexpansion of the reinforcement, thereby causing it to be subjected toradial compression. With this arrangement, the reinforcement is confinedin the space between the expanding inner portion and the flexible outercasing. The radially expanding inner portion operates in conjunctionwith the flexible outer casing to confine the reinforcement and alsocauses the volume of the space in which the reinforcement is confined toprogressively decrease. This forces the binder within the reinforcementto fully impregnate the reinforcement; that is, the layers ofreinforcing fabric become fully “wetted-out”. In particular, it providesa compaction force to the reinforcement and effectively pumps the binderthrough the layers of reinforcing fabric to distribute the binder withinthe space in a controlled and constrained manner.

Further, the progressive decrease in volume of the space in which thereinforcement is confined may act to positively expel air from withinthe space which has the effect of enhancing impregnation of the binderwithin the reinforcement.

The outer casing and the various reinforcing fabric tubular layers maybe adapted to facilitate the expulsion of the air. The outer casing andthe various reinforcing fabric tubular layers may be configured tofacilitate expulsion of air, for example, the outer casing and thevarious reinforcing fabric tubular layers may incorporate vents atintervals along their respective lengths to facilitate expulsion of theair. Additionally, or alternatively, the fibrous layer of the outercasing which provides the breather layer may facilitate displacement ofair, typically upwardly and along the assembly to a release or ventingpoint.

The flexible outer casing may have some resilience in order to yieldingresist radial expansion of the reinforcing fabric tubular layers atleast to some extent. However, the flexible outer casing typically hasless resilience than the inner tube. In this way, the flexible outercasing can cushion the initial stage of the radial expansion of thereinforcing fabric tubular layers. In particular, the flexible outercasing has some elasticity. The flexible outer casing may have someelasticity for the purpose of enhancing control of the rate at which thebinder progressively wets the reinforcement.

Another example embodiment is directed to a method of constructing anelongate hollow structure comprising a radially inner portion and aradially outer portion, with the two portions merging together toprovide an integrated tubular wall structure, the method comprising:providing the radially inner portion comprising inner tube comprising aninner liner with a fibrous layer bonded onto one face thereof;assembling the radially outer portion about the radially inner portion;and expanding the inner portion; wherein the outer portion comprises anouter tube of fibre reinforced composite construction surrounded by aflexible outer casing and wherein the inner portion comprises an innertube comprising an inner liner with a fibrous layer bonded onto one facethereof, whereby resinous binder impregnating the outer tube alsoimpregnates the fibrous layer to integrate the outer portion with theinner portion.

Another example embodiment is directed to a method of constructing anelongate hollow structure comprising forming a flexible tubular wallstructure about a central portion, expanding the central portion tocause the tubular wall structure to assume a prescribed cross-sectionalprofile, and hardening, curing or otherwise setting the tubular wallstructure.

The central portion may comprise part of the wall structure.

The flexible wall structure may comprise a fibre-reinforced plasticcomposite.

The flexible wall structure may further comprise settable plastic suchas a resinous binder. Typically, the settable plastic comprises acurable resin.

The fibre reinforced plastic composite may comprise reinforcementconfigured as a fabric incorporating reinforcement fibres.

In an example, the reinforcing fabric has quadraxial fibre orientations.The quadraxial fibre orientations offer hoop and axial stress bearingproperties.

The flexible tubular wall structure may further comprise a flexibleouter casing surrounding the fibre-reinforced plastic composite.

The expandable central portion may comprise an inner tube which providesan inflatable bladder to expand the flexible tubular wall structureprior to hardening, curing or other setting thereof.

In an example, the inner tube is integrated with and forms part of thetubular wall structure.

The continuous movement and then expansion of the flexible tubular wallstructure serves to pre-stress and align fibres within the reinforcingfabric to enhance hoop stress bearing properties over the entire lengthof the elongate hollow structure under construction.

In an example, the reinforcing fabric is also pre-stressed axially(linearly) to enhance tensile load bearing properties.

The central portion may be configured as a bladder.

The bladder may be inflated using a fluid medium such as air or water.

In an example, the bladder is expandable elastically.

In one arrangement, the tubular structure may be of a specific length.The tubular structure may, for example, comprise a tubular element suchas a pipe made to a specific length.

In another arrangement, the tubular structure may be formedprogressively to any desired length. The tubular structure may, forexample, comprise a tubular element such as a pipe formed continuouslyuntil the desired length is attained. In this regard, the pipe may be ofa length to constitute a continuous pipe providing a pipeline extendingbetween two distant locations.

In contrast to the prior art arrangement where a pipeline extendingbetween two distant locations would typically comprise a plurality ofpipe sections joined one to another, the pipe according to the firstaspect of the invention can permit the pipeline to be formed as onecontinuous pipe.

Another example embodiment is directed to a method of constructing anelongate hollow structure comprising forming a flexible tubular wallstructure having an interior, inflating the interior of the flexibletubular wall structure to provide form and shape thereto; and hardening,curing, or otherwise setting the flexible wall structure to provide thetubular element.

The flexible wall structure may comprise a fibre-reinforced plasticcomposite which can cure to provide the tubular element.

The flexible wall structure may further comprise a flexible outer casingsurrounding the fibre-reinforced plastic composite.

In certain applications the fibre-reinforced plastic composite cures toa rigid condition. In certain other applications the fibre-reinforcedplastic composite cures to a more flexible condition.

The tubular wall structure may comprise a liner having a fluidimpervious inner surface. The inner surface may be defined by a highgloss material such as a polyurethane liner.

Another example embodiment is directed to a method of constructing apipe comprising forming a flexible tubular wall structure comprising afibre-reinforced plastic composite, inflating the interior of theflexible tubular wall structure to provide form and shape thereto; andhardening, curing or otherwise setting the flexible wall structure toprovide the pipe.

The pipe may be constructed on a continuous basis and progressivelyinstalled in position prior to curing of the flexible wall structure,whereby the flexible wall structure cures once in the installed positionof the pipe.

Another example embodiment is directed to a method of constructing apipe on a continuous basis, comprising forming a flexible tubular wallstructure comprising a radially inner portion and a radially outerportion, the radially inner portion comprising an inner tube, theradially outer portion comprising an outer tube of fibre-reinforcedcomposite construction and a flexible outer casing surrounding the outertube, inflating the inner tube to provide form and shape thereto; andcuring the flexible wall structure to provide the pipe. There is a spacebetween the inner tube and the flexible outer casing. The fibrereinforced composite construction comprises reinforcement and a binderand is located between the inner tube and the flexible outer casing. Theflexible outer casing serves to resist radial expansion of the innertube causing it to be subjected to radial compression, and the radiallyexpanding inner tube operates in conjunction with the flexible outercasing to cause the volume of the space between the inner tube and theflexible outer casing to progressively decrease, thereby causing thebinder to spread through the space between the inner tube and theflexible outer casing.

In this example method, the flexible wall structure may comprise innerand outer portions, wherein the method further comprises forming theinner portion to define an inner tube and forming an outer tube of fibrereinforced composite construction about the inner tube to define theouter portion.

The outer tube may be formed using one or more layers of reinforcingfabric, wherein the method further comprises configuring each layer as atubular layer disposed about the inner tube, impregnating the tubularlayers with a resinous binder, inflating the inner tube to provide formand shape to the tubular wall structure, and curing the resinous binderto harden the tubular wall structure.

The flexible outer casing is installed around the tubular layers ofreinforcing fabric to contain the resinous binder.

The flexible outer casing may be formed of any appropriate material,including for example polyethylene.

More particularly, the outer casing comprises an outer layer ofpolyethylene and a fibrous layer bonded onto one face thereof, thearrangement being that the fibrous layer confronts the reinforcement, asdescribed above.

The outer casing may remain in place and ultimately form an integralpart of the tubular structure, or it may be subsequently removed afterhaving served its purpose.

The exterior of the outer layer of the outer casing may be configured toadherence to a surrounding protective sheath, such as a concrete casing.This may comprise a surface roughness or formations such as tufts on theexterior of the outer layer of the outer casing.

The inner tube may comprise an inner liner with a fibrous layer bondedonto one face thereof, and the resinous binder impregnating thereinforcing fabric may also impregnate the fibrous layer to integratethe outer portion with the inner portion.

The pipe may be constructed in a mobile installation plant configured asa vehicle which can move in relation to an installation site such thatthe continuously formed pipe can be progressively delivered to theinstallation site.

Another example embodiment is directed to a method of constructing apipe in a flexible condition, laying the pipe at an installation site,and allowing the flexible pipe to transform into a rigid condition atthe installation site.

The installation site may comprise a trench into which the pipe isprogressively laid in the flexible condition. The pipe may be laiddirectly into the trench or placed alongside the trench and subsequentlyinstalled in the trench. The trench may have a foundation of sand orother material shaped to provide a curved depression upon which the pipeis laid for support.

The pipe may be assembled in a mobile installation plant which can movewith respect to the installation site, laying the pipe in the flexiblecondition.

Another example embodiment is directed to an elongate hollow structureof composite construction, comprising a radially inner portion and aradially outer portion, wherein the two portions merge together toprovide an integrated tubular wall structure. The radially outer portioncomprises an outer tube of fibre reinforced composite constructionincluding reinforcement. The radially outer portion further comprises aflexible outer casing that serves to resist radial expansion of thereinforcement, thereby causing it to be subjected to radial compression.The fibre reinforced composite construction comprises the reinforcementand a binder and is located between the inner portion and flexible outercasing. The flexible outer casing serves to resist expansion of theinner portion causing the inner portion to be subjected to compression,and the binder is spread between the inner portion and flexible outercasing due to the expansion of the inner portion, operating inconjunction with the flexible outer casing to cause the volume of thespace between the inner portion and the flexible outer casing toprogressively decrease during the formation of the elongate hollowstructure, thereby causing the binder to spread through the spacebetween the inner portion and the flexible outer casing.

The reinforcement may comprise one or more layers of reinforcing fabric,each configured as a tube disposed about the inner portion. Thereinforcement may comprise a plurality of layers, each configured as arespective tube disposed one about another.

The reinforcing fabric may comprise reinforcing fabric whichincorporates reinforcement fibres featuring quadraxial fibreorientations. The reinforcement fibres may comprise glass fibres. Thequadraxial fibre orientations offer the necessary hoop and axial stressbearing properties to the tubular structure.

The inner portion may comprise an inner liner with a fibrous layerbonded onto one face thereof. The other face of the liner may define theinterior surface of the tubular structure.

The resinous binder impregnating the reinforcing fabric may alsoimpregnate the fibrous layer bonded on the inner liner to integrate theouter portion with the inner portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will become more fully understood from the detaileddescription given herein below and the accompanying drawings, whereinlike elements are represented by like reference numerals, which aregiven by way of illustration only and thus are not limitative of theexample embodiments herein.

FIG. 1 is a schematic view of a pipe according to a first embodimentunder construction.

FIG. 2 is a schematic cross-sectional schematic view of the pipe shownin FIG. 1.

FIG. 3 is a schematic fragmentary side view of a section of the pipe.

FIG. 4 is a schematic cross sectional view of the inner portion of thepipe.

FIG. 5 is a schematic view of reinforcing fabric incorporatingreinforcement fibres featuring quadraxial fibre orientations used in theconstruction of the outer portion of the pipe.

FIG. 6 is a schematic cross sectional view of a reinforcing fabrictubular layer formed from the reinforcing fabric shown in FIG. 5 andused in the construction of the outer portion of the pipe, the tubularlayer being shown in a partly assembled condition

FIG. 7 is a view similar to FIG. 6, except that the tubular layer isshown in an assembled condition.

FIG. 8 is a schematic cross-sectional view of an assembled tubularstructure from which the pipe according to the first embodiment isconstructed, the tubular structure being shown in a radially expanded(inflated) condition.

FIG. 9 is a view similar to FIG. 8, with the exception that there isshown provision for venting air from a space within the assembledtubular structure.

FIG. 10 is also a view similar to FIG. 8, with the exception that thetubular structure is shown in a collapsed (uninflated) condition.

FIG. 11 is a schematic cross-sectional view of an inner tube formingpart of the assembled tubular structure, the inner tube being showncollapsed into a flattened condition.

FIG. 12 is a schematic cross-sectional view of the assembled tubularstructure from which the pipe according to the first embodiment isconstructed, the tubular structure being shown with the inner tube beingfolded using a different folding pattern.

FIG. 13 is a schematic cross-sectional view of the inner tube formingpart of the assembled tubular structure shown in FIG. 12, with the innertube being shown in a folded condition.

FIG. 14 is a view similar to FIG. 13, excepted that the inner tube beingis shown in a partly flattened condition.

FIG. 15 is a view similar to FIG. 13, excepted that the inner tube beingis shown in a fully flattened condition.

FIG. 16 is a schematic perspective view of an assembly system forassembling the tubular layers depicted in FIG. 7.

FIG. 17 a schematic perspective view of a guide system for progressivelymoving a strip of reinforcing fabric as shown in FIG. 5 through atransition from the first (flat) condition to the second (tubular)condition.

FIG. 18 a schematic perspective view of a bonding system for securingoverlapping edges of the strip of reinforcing fabric together toestablish a joint to retain the strip in the second (tubular) condition.

FIG. 19 is a schematic view of an assembly line for the pipe and is intwo parts, being FIGS. 19A and 19B.

FIG. 20 is a schematic sectional view of one end section of the pipeduring fabrication thereof, with an end fitting installed on that endsection.

FIG. 21 is a schematic side view of the other end section of the pipeduring fabrication thereof, with an end fitting installed on that endsection.

FIG. 22 is a schematic sectional view of the end section of the pipeshown in FIG. 21, together with an associated profile forming system.

FIG. 23 is a schematic view of an assembly line for a pipe according toa second embodiment and is in two parts, being FIGS. 23A and 23B.

FIG. 24 is a fragmentary view of part of the assembly line of FIG. 23.

FIG. 25 is a cross-section on line 25-25 of FIG. 23B.

FIG. 26 is a cross-section on line 26-26 of FIG. 23B.

FIG. 27 is a cross-section on line 27-27 of FIG. 23B.

FIG. 28 is a cross-section on line 28-28 of FIG. 23B.

FIG. 29 is a cross-section on line 29-29 of FIG. 23B.

FIG. 30 is a cross-section on line 30-30 of FIG. 23B.

FIG. 31 is a cross-section on line 31-31 of FIG. 23B.

FIG. 32 is a schematic view of an assembly line for a pipe according toa third embodiment.

FIG. 33 is a schematic view of part of the assembly line of FIG. 32,illustrating sets of elements for pinching the assembled tube structureand an outer casing therearound.

FIG. 34 is a fragmentary view of part of the assembly line of FIG. 32.

FIG. 35 is a cross-section on line 35-35 of FIG. 34.

FIG. 36 is a cross-section on line 36-36 of FIG. 34;

FIG. 37 is a cross-section on line 37-37 of FIG. 34.

FIG. 38 is a cross-section on line 38-38 of FIG. 34.

FIG. 39 is a cross-section on line 39-39 of FIG. 34.

FIG. 40 is a cross-section on line 40-40 of FIG. 34.

FIG. 41 is a schematic cross-sectional view of the assembled tubestructure and an outer casing therearound, illustrating a conditionapproaching full immersion in resinous binder.

FIG. 42 is a view similar to FIG. 41 but illustrating full immersion inresinous binder.

FIG. 43 is a fragmentary cross-sectional view of the arrangementdepicted in FIG. 39.

FIG. 44 is a schematic view of part of an assembly line for a pipeaccording to a fourth embodiment.

FIG. 45 is a schematic view of part of an assembly line for a pipeaccording to a fifth embodiment.

FIG. 46 is a schematic perspective view of apparatus used in theassembly line shown in FIG. 45, the apparatus being provided tofacilitate a relatively rapid wet-out of the reinforcement used infabrication of the pipe.

FIG. 47 is an elevational view of a roller array used in the apparatusshown in FIG. 46.

FIG. 48 is a fragmentary schematic view depicting a tubular structureassembled during fabrication of the pipe being subjected to manipulationakin to a peristaltic pressing action by the apparatus shown in FIG. 46.

FIG. 49 is a fragmentary side view depicting a section of a pipeaccording to a sixth embodiment, the section being configured as astraight section.

FIG. 50 is a fragmentary side view depicting a further section of thepipe according to a sixth embodiment, the section being configured as abend section.

FIG. 51 is a fragmentary side view depicting a further section of thepipe according to a sixth embodiment, the section being configured as afurther bend section.

FIG. 52 is a fragmentary side view depicting the further section of thepipe shown in FIG. 51 prior to bending thereof to form the further bendsection.

FIG. 53 is a schematic view of part of an assembly line for a pipeaccording to a seventh embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1 to 22 of the drawings, a first example embodimentof the invention is directed to an elongate hollow structure in the formof a tubular element configured as a pipe 10, and to a method ofconstruction of the pipe on a continuous basis.

The pipe 10 is of composite construction, comprising a radially innerportion 11 and a radially outer portion 13, with the two portions 11, 13merging together to provide an integrated tubular wall structure. In thearrangement illustrated, the outer portion 13 is encased within aprotective sheath 14 comprising a hardenable composition 16 such ascement or concrete contained by an outermost skin 18 of any suitablematerial; such as geotextile cloth. The protective sheath 14 is intendedto afford protection to the pipe 10 against compression loading to whichit might be exposed once in the installed condition.

The inner portion 11 comprises an inner liner 15 with a layer 17 ofresin absorbent material bonded onto one face thereof. The other face ofthe liner 15 defines the interior surface 19 of the pipe 10. Typically,the liner 15 presents a high gloss surface at the inner face 19. Theinner liner 15 may, for example, comprise polyurethane, polyethylene orany other resiliently flexible material which is preferably alsoimpervious to air and also compatible to fluid to be conveyed within thepipe 10. The resin absorbent layer 17 may, for example, comprise felt orflock.

As best seen in FIG. 4, the inner portion 11 is configured as an innertube 21 formed from a longitudinal strip 23 having longitudinal sideedges 25. The strip 23 is rolled longitudinally into a tubularconfiguration to provide the inner tube 21, with the longitudinal edges25 in abutting relationship to provide a butt joint 26. An innerjointing strip 27 is applied to the inner side of the inner tube 21 andan outer jointing strip 28 is applied to the outer side of the innertube 21, with the two jointing strips 27, 28 bridging the butt joint 26and providing a continuous, fluid tight connection between the abuttinglongitudinal side edges 25. In FIG. 4, the jointing strips 27, 28 areshown spaced from the butt joint 26 for the purposes of clarity, but inpractice are actually in contact with the butt joint.

The inner tube 21 defines an inflatable bladder 24 having an inflationcavity 29, the purpose of which will be explained later.

The outer portion 13 is configured as an outer tube 30 of fibrereinforced composite construction surrounded by a flexible outer casing31. More particularly, the outer tube 30 comprises reinforcement 32impregnated in a resinous binder. The flexible outer casing 31 isinstalled around the tube 30 to contain the resinous binder, as will bedescribed in more detail shortly. The flexible outer casing 31 may beformed of any appropriate material, including for example polyethylene.The outer casing 31 may remain in place and ultimately form an integralpart of the pipe 10, or it may be subsequently removed after havingserved its purpose.

The outer casing 31 comprises an outer layer of polyethylene and afibrous layer bonded onto one face thereof, the arrangement being thatthe fibrous layer confronts the reinforcement 32. The fibrous layerprovides a breather layer and also is ultimately impregnated with theresinous binder for integration of the assembly.

The resinous material which provides the resinous binder may be of anyappropriate type; a particularly suitable resinous material comprisesthermosetting resin such as epoxy vinyl ester or other suitable resinand thermoplastic resin systems.

The reinforcement 32 comprises one or more layers 33 of reinforcingfabric 34 (as shown in FIG. 5), each layer being configured as areinforcing fabric tubular layer 35 (as shown in FIG. 7) disposed aboutthe inner tube 21. In this embodiment, there is a plurality of layers 33configured as the respective tubular layers 35 disposed one aboutanother (and hence also disposed about the inner tube 21 as previouslymentioned and as shown in FIG. 8). Adjacent fabric layers 33 may bebonded together in any suitable way such as by a hot welding chemicalbonding, and/or mechanical fixing such as by stitching or stapling.

The reinforcing fabric 34 comprises reinforcing fabric whichincorporates reinforcement fibres featuring quadraxial fibreorientations, as shown in FIG. 5. The reinforcement fibres compriseaxial fibres 36 a (at an angle approaching the pipe axis, which isdepicted by line 37 in FIG. 3), transverse fibres 36 b (at an angleapproaching 90 degrees to the pipe axis) and angular fibres 36 c (at anangle approaching 45 degrees to the pipe axis). The reinforcement fibresmay comprise glass fibres. The quadraxial fibre orientations offer thenecessary hoop and axial stress bearing properties to the pipe.

Each reinforcing fabric tubular layer 35 is assembled from a strip 41 ofreinforcing fabric material having longitudinal edges 43 which arebrought together in overlapping relationship at joint 44 to form thetubular layer 35. The overlapping edges 43 are secured together in anyappropriate way to maintain the tubular formation. In this embodiment,the overlapping edges 43 are secured together by hot melt welding usinga hot melt adhesive. In FIG. 6, the overlapping edges 43 are shownspaced apart for the purposes of clarity, but in practice are actuallyin contact with each other to provide the joint 44, as shown in FIG. 7.The structural integrity of the joint 44 is subsequently established bythe impregnation of resinous binder into the reinforcing fabric 34 fromwhich the respective tubular layer 35 is formed. Specifically, theresinous binder impregnates the overlapping edges 43 and bonds themtogether to supplement and supplant the initial bond established by thehot melt adhesive.

The various tubular layers 35 are oriented such that the respectivejoints 44 are offset with respect to each other, as shown in FIG. 8. Inthe arrangement shown in the drawings, the tubular layers 35 areoriented such that the respective joints 44 are disposed towards theunderside 46 of the pipe 10 under construction. This may be advantageousas the underside 46 is the area in which resinous binder is likely to beplentiful to enhance the bond between the overlapping edges 43 at eachjoint 44.

The resinous binder impregnating the reinforcing fabric 34 alsoimpregnates the layer of felt 17 on the inner liner 15 to integrate theouter portion 13 with the inner portion 11.

The reinforcing fabric tubular layers 35 are impregnated with theresinous binder after the tubular layers 35 have been disposed one aboutanother (see for example tubular layers 35 a, 35 b, 35 c in FIG. 8) andhence also about the inner tube 21 as previously described. In analternative arrangement, the reinforcing fabric tubular layers 35 may beimpregnated with resinous binder after each tubular layer 35 has beenassembled. Each assembled reinforcing fabric tubular layer 35 may beattached to the preceding inner reinforcing fabric tubular layer 35,such as by hot melt welding. However, it may be preferable to not attachthe adjacent reinforcing fabric tubular layers 35, so that each can movefreely relative to the others for transfer of loads and stress wherebyeach layer 35 can accept its share of the load.

Typically, air is removed from the reinforcing fabric tubular layers 35prior to impregnation with the resinous binder.

After the reinforcing fabric tubular layers 35 have been impregnatedwith the resinous binder, but prior to curing thereof, the inflatablebladder 24 defined by the inner tube 21 is inflated by introduction ofan inflation fluid such as air into the inflation cavity 29. This causesthe inflatable bladder 24 to expand radially towards the flexible outercasing 31, providing form and shape to the surrounding outer portion 13.In particular, the outer portion 13 assumes a circular profile incross-section.

The continuous expansion of the inflation cavity 29 within theinflatable bladder 24 as it moves through a compression device 125 (seeFIG. 19B) stretches the reinforcing fabric tubular layers 35 in alldirections, serving to enhance hoop stress and axial stress bearingproperties of the pipe 10. In particular, the expansion serves topre-stress fibres within the reinforcing fabric tubular layers 35 toenhance hoop stress bearing properties and also axially tensions thereinforcing fabric tubular layers to pre-stress fibres therein axiallyto enhance tensile load bearing properties of the pipe 10.

The flexible outer casing 31 serves to resist radial expansion of thereinforcing fabric tubular layers 35, thereby causing the reinforcement32 to be subjected to radial compression. With this arrangement, thereinforcement 32 (which as previously noted comprises one or more layers33 of reinforcing fabric 34, each layer being configured as areinforcing fabric tubular layer 35, as shown in FIG. 12), is confinedin the space 45 between the expanding inner tube 21 and the flexibleouter casing 31. The radially expanding inner tube 21 operates inconjunction with the flexible outer casing 31 to confine thereinforcement 32 and also causes the volume of the space 45 in which thereinforcement 32 is confined to progressively decrease. This forces theresinous binder within the reinforcement 32 to fully impregnate thereinforcement 32; that is, the layers 33 of reinforcing fabric 34configured as the tubular layers 35, become fully “wetted-out”. Inparticular, it provides a compaction force to the reinforcement 32 andeffectively pumps the resinous binder through the layers 33 ofreinforcing fabric 34 to distribute the resinous binder within the space45 in a controlled and constrained manner. It is a particular feature ofthe embodiment that the step of delivering resinous binder to thereinforcement and the step of fully wetting out the reinforcement 32with the resinous binder are separate and distinct actions.

Further, the progressive decrease in volume of the space 45 in which thereinforcement 32 is confined acts to positively expel air from withinthe space 45 which has the effect of enhancing impregnation of theresinous binder within the reinforcement 32. The outer casing 31 and thevarious reinforcing fabric tubular layers 35 may be adapted tofacilitate the expulsion of the air. The breather layer defined by thefibrous inner layer of the outer casing 31 facilitates this expulsion ofair. Further, the outer casing 31 and the various reinforcing fabrictubular layers 35 may, for example, incorporate vents at intervals alongtheir respective lengths to facilitate expulsion of the air, as shown inFIG. 9. In one arrangement, the vents 48 may comprise perforations, suchas puncture holes, formed in the outer casing 31 and the variousreinforcing fabric tubular layers 35. With such an arrangement, theperforations are ultimately sealed by the resinous binder to ensure thesealed integrity of the pipe 10. In another arrangement, the vents maycomprise ports inserted in the outer casing 31 and the variousreinforcing fabric tubular layers 35. The ports may, for example,comprise tubular inserts formed of a material which dissolves orotherwise degrades upon exposure to the resinous binder. With such anarrangement, the apertures in which the ports were accommodated areultimately sealed by the resinous binder to ensure the sealed integrityof the pipe 10.

The flexible outer casing 31 may have some resilience in order toyielding resist radial expansion of the reinforcing fabric tubularlayers 35 at least to some extent. In this way, the flexible outercasing 31 can cushion the initial stage of the radial expansion of thereinforcing fabric tubular layers 35. In particular, it is desirablethat the flexible outer casing 31 have some elasticity. The flexibleouter casing 31 may have some elasticity elastic for the purpose ofenhancing control of the rate at which the progressively rising pool ofresinous binder progressively wets the reinforcement 32. If, on the onehand, the resinous binder rises within the space 45 too rapidly, it maybe that full wet-out of fibres in the reinforcement 32 is not achieved.If, on the other hand, the resinous binder rises within the space 45 tooslowly, it may be that the resinous binder could commence to cure beforefull wet-out of fibres in the reinforcement 32 is achieved.

The elastic nature of the flexible outer casing 31 installed around theassembled around the reinforcement 32 functions somewhat as a girdle forcontrolling external pressure exerted on the rising pool of resinousbinder. The elastic characteristic of the flexible outer casing 31 isselected to achieve the desired rate of wet-out. The elastic forceexerted by the outer casing 31 provides some counterbalancing of thetension exerted by the inflating bladder 24 defined by the inner tube21.

The inflatable bladder 24 is maintained in the inflated condition untilsuch time as the resinous binder has hardened sufficiently to maintainthe form and shape of the pipe, after which the inflation fluid can bereleased from the inflation cavity 29. The pipe 10 thus is formed, withthe inner liner 15 defining the central flow passage within the pipe.

The inner tube 21 may be preformed, or may be assembled on site as partof the construction process for the pipe 10.

In circumstances where the inner tube 21 is preformed, it may bedelivered to site in a collapsed condition. The inner tube 21 may becollapsed in any appropriate way. Typically, the inner tube 21 canassume a collapsed condition by being folded in a folding pattern toprovide a compact arrangement in cross-sectional profile. In thearrangement shown in FIGS. 10 and 11, the inner tube 21 is collapsedinto a flattened condition in cross-sectional profile using a foldingpattern which defines two longitudinal side portions 51 and foldportions 52 therebetween. With this arrangement, the longitudinal sideportions 51 can be in abutting contact with each other to provide acompact formation. In the arrangement shown in FIGS. 12 to 15, the innertube 21 is collapsed into a flattened condition in cross-sectionalprofile using a folding pattern which defines two longitudinal sideportions 53 and re-entrant fold portions 54 therebetween. With thisarrangement, the re-entrant fold portions 54 each extend inwardly fromone longitudinal side of the collapsed inner tube 21. FIG. 13 is aschematic cross-sectional view of the inner tube 21 shown in a foldedcondition. In FIG. 14, the inner tube 21 is shown in a partly flattenedcondition. In FIG. 15, the inner tube is shown in a fully flattenedcondition. The inner tube 21 assumes the various conditions at variousstages during fabrication of the pipe 10.

The reinforcement 32 is assembled about the inner tube 21. Inparticular, the reinforcing fabric tubular layers 35 are assembledsequentially about the inner tube 21. As described above, eachreinforcing fabric tubular layers 35 is assembled from a respectivestrip 41 of reinforcing fabric material having longitudinal edges 43which are brought together in overlapping relationship at joint 44 toform the tube structure.

The various tubular layers 35 are arranged in a series 36 comprising aninnermost tubular layer 35 a, an outermost tubular layer 35 b, and oneor more intervening tubular layers 35 c disposed between the innermosttubular layer 35 a and the outermost tubular layer 35 b. The tubularlayers 35 in the series are of progressively increasing diameters inorder to provide a good fit and alignment one with respect to anotherand thereby afford some precision in the construction of the pipe 10. Inorder to accommodate the progressively increasing diameters between thetubular layers 35, the respective strips 41 of reinforcing fabricmaterial need to be of different widths, with the widths progressivelyincreasing from the innermost tubular layer 35 a to the outermosttubular layer 35 b. Each tubular layer 35 is designed to be inflated,unfolded or unfurled to its maximum diameter by the inflation force ofthe fluid pressing against the inner tube 21 to provide the fullexpansion of the assembly and the fibres within it to hold the loads ofthe pipe 10 in operation.

As described above, the various tubular layers 35 in the series 36 areoriented such that the respective joints 44 are offset with respect toeach other, as best seen in FIG. 8.

Each tubular layer 35 is assembled from its respective strip 41 byprogressively moving the strip through a transition from a firstcondition in which the strip is flat to a second condition in which thestrip is in a tubular configuration with the edges 43 in overlappingrelation. In FIG. 16 of the drawings, the strip 41 is depicted with asection 41 a thereof in the first (flat) condition and a further section41 b thereof in the second (tubular) condition. In the first condition,the strip 41 can be stored in roll form 55 on a reel 56, as shown inFIG. 16.

An assembly system 60 is provided for progressively moving therespective strip 41 through the transition from the first (flat)condition to the second (tubular) condition and for securing theoverlapping edges 43 together to establish the joint 44 and thus formthe tubular layer 35. As the strip 41 moves through the transition fromthe first (flat) condition to the second (tubular) condition itprogressively envelopes the inner tube 21.

The assembly system 60 comprises a guide system 61 for progressivelymoving the respective strip 41 through the transition from the first(flat) condition to the second (tubular) condition. The guide system 61,which is best seen in FIG. 17, comprises a guide 62 comprising a body 63defining an entry end 64, an exit end 65 and a guide path 66 extendingbetween the entry end and the exit end. The body 63 is configured as atubular structure 67 having longitudinal marginal edge portions 68 whichare disposed in overlapping relation and spaced apart to define alongitudinal gap 69 therebetween. The tubular structure 67 is configuredsuch that the guide path 66 tapers inwardly from the entry end 64 to theexit end 65. With this arrangement, the tubular structure 67 provides atapering guide surface 67 a which is presented to the respective strip41 as it advances along the guide path 66 from the entry end 64 to theexit end 65 and which progressively moves the strip 41 through thetransition from the first (flat) condition at the entry end 64 to thesecond (tubular) condition at the exit end. As the strip 41 advancesalong the guide surface 67 a, the longitudinal marginal edges 43 of thestrip are progressively turned inwardly by the tapering profile, withone of the longitudinal marginal edges 43 of the strip 41 partiallyentering the longitudinal gap 69 in the tubular structure 67 and theother of the longitudinal marginal edges 43 overhanging the innermarginal edge 68 a. With this arrangement, the longitudinal edges 43 areprogressively brought together in overlapping relationship in readinessto be secured together to establish the joint 44 and complete formationof the tubular layer 35.

As the strip 41 is being assembled into the tubular configuration toform the tubular layer 35, the inner tube 21 is also moving along theguide path 66 from the entry end 64 and the exit end 65. In this way,the tubular layer 35 can be assembled about the inner tube 21 andthereby envelopes it.

Similarly, the innermost intervening tubular layer 35 c can be assembledabout tubular layer 35 a and the inner tube 21 about which the latter isformed, and then any other intervening tubular layers 35 c andultimately the outermost tubular layer 35 b can be assembled about thepreceding tubular layers 35.

The tubular structure 67 may incorporate means for attracting andholding the strip 41 against the guide surface 67 a. Such means maycomprise a suction system incorporating a plurality of holes in theguide surface 67 a to which suction is applied to draw the strip 41 intocontact with the guide surface as the strip moves along the guide path66.

The assembly system 60 further comprises a guide roller 70 about whichthe respective strip 41 turns in its path from the reel 56 to the entryend 64 of the tubular structure 67 in order to align the strip 41correctly for entry into the tubular structure 67.

The assembly system 60 further comprises a bonding system 71 forsecuring the overlapping edges 43 together to establish the joint 44 andthus complete formation of the tubular layer 35. The bonding system 71,which is shown in FIG. 18, comprises means 72 for applying hot meltadhesive between the overlapping edges 43 and then bringing the edgestogether to establish the joint 44. In the arrangement shown, such means72 comprises a delivery head 73 for delivering one or more bands 74 ofhot melt adhesive between the overlapping edges 43. The delivery head 73is adapted to receive a supply of hot melt adhesive from a source 75 byway of a delivery line.

The bonding system 71 further comprises means 76 for bringing theoverlapping edges 43 together with the hot melt adhesive therebetween toestablish the joint 44. In the arrangement shown, such means 76comprises a press 77 for pressing the overlapping edges 43 together. Thepress 77 comprises two cooperating press rollers 78 between which theoverlapping edges 43 pass to be pressed together to establish the joint44 by way of the hot melt adhesive. While not shown in the drawings, theassembly system 60 may further comprise means for facilitating rapidsetting of the holt melt adhesives Such means may comprise anarrangement to deliver a cooling agent, such as cold air, to the area atand around the joint 44.

The construction process of the pipe 10 according to the embodiment willnow be described in more detail. In this embodiment, the pipe 10 isconstructed on a continuous basis and progressively laid into a trench79 which has been dug to receive the pipe. The pipe 10 is laid in thetrench 79 prior to curing of the resinous binder which impregnates thereinforcing fabric 34 and also the layer of felt 17 on the inner liner15. The curing occurs after laying of the pipe 10 within the trench 79.In this way, the pipe 10 is in a flexible condition to facilitate itbeing guided into the trench and laid into position, and hardens once inposition.

Referring in particular to FIG. 1, the pipe 10 is assembled in a mobileinstallation plant 80 configured as a vehicle which can travel alongsidethe trench 79 such that the continuously formed pipe 10 can “snake” fromthe mobile installation plant 80 into the trench 79. The pipe 10 may becured within the trench 79 is any appropriate way. In the arrangementillustrated, a curing unit 81 is provided to progressively move alongthe trench 79 to expose the recently laid section of the pipe to acuring action. The curing unit 81 may, for example, apply heat or otherradiation such as UV radiation or light (according to the nature of theresinous binder) to the pipe 10 to facilitate the curing process. In analternative arrangement, the resinous binder may incorporate anappropriate catalyst to cure the pipe in ambient conditions.

The mobile installation plant 80 comprises a pipe assembly line 82, asshown in FIG. 19 (which is presented in two parts, FIGS. 19A and 19B).

Referring to FIG. 19A, the assembly line 82 comprises a supply ofmaterial 83 in strip form and stored on a roll 85. The material 83provides the inner liner 15 with the layer of resin absorbent material17 bonded thereto. The material 83 is progressively unwound from theroll 85 and conveyed as a strip 23 to a first assembly station 87 atwhich it is formed into the inner tube 21. As described previously, thestrip 23 is rolled longitudinally into a tubular configuration toprovide the inner tube 21, with the longitudinal edges 25 in abuttingrelationship to provide the butt joint 26, and the jointing strip 27applied to the inner side of the inner tube 21 to bridge the butt joint26 and provide a continuous, fluid tight connection.

The assembly line 82 further comprises one or more supplies of material91, each in strip form and stored in roll form 55 on respective reels56. In the arrangement shown in FIG. 19A there are two reels 56, butother numbers are possible. The material 91 provides the reinforcingfabric 34 incorporating reinforcement fibres featuring quadraxial fibreorientations. The material 91 is progressively unwound from therespective reel 56 and conveyed as strip 41 to a second assembly station95 at which it is formed into the respective reinforcing fabric tubularlayer 35 about the inner tube 21. As described previously, eachreinforcing fabric tubular layer 35 is assembled from the strip 41 ofreinforcing fabric material having longitudinal edges 43 which arebrought together in overlapping relationship to form the tubular layer.The overlapping edges 43 are secured together in to maintain the tubularformation. In this embodiment, the overlapping edges 43 are securedtogether by hot melt welding. The respective tubular layers 35 aredisposed one about another and also disposed about the inner tube 21 aspreviously mentioned. Adjacent fabric layers 33 may be bonded togetherby a hot welding or chemical bonding process. The layers may comprise abonding or forming material to more effectively hold the layerstogether. This may for example comprise chop strand mat, felt or veil toenhance the laminar shear between the layers of high strength quadraxialfabric and allow for easier release of air from the laminate.

The reinforcing fabric tubular layers 35 and the inner tube 21 provide atube structure 100. The tube structure 100 is conveyed to a thirdstation 103 at which it is compressed between compression rollers 105 toextract air therefrom and force the resinous binder into direct contactwith the reinforcement 32 and the adjacent layer 17 of resin absorbentmaterial.

The tube structure 100 is then conveyed to a fourth station 105 at whichit is impregnated with the resinous binder. In the illustratedarrangement, the tube structure 100 is passed through a resin bath 107,circulating between rollers 109 to work the resinous binder into thefelt 17 and the reinforcing fabric 34. At least some of the rollers 109are driven to assist movement of the tube structure 100.

The tube structure 100 is then conveyed to a fifth station 111 at whichis engaged by doctor rollers 113 to remove excess resinous binder whichcan be collected in a catchment zone 115.

The tube structure 100, which is now impregnated with resinous binder,is then conveyed to a sixth station 117 at which the flexible outercasing 31 is installed to complete assembly of the tube structure 100.Referring now to FIG. 19B, the assembled tube structure 100 is thenconveyed to a seventh station 121 at which there is provided thecompression device 125 comprising two endless drives 127 defining apassage 129 through which the tube structure 100 can pass. The assembledtube structure 100 is compressed in the passage 129 to define a chokedzone 123 blocking the passage of air along the interior of the assembledtube structure. The two endless drives 127 incorporate opposing elements131 such as cleats which cooperate to pinch the tube structure 100 atintervals and close it against the passage of air while allowing theimpregnated resinous binder within the tube structure to pass throughthe choke passage 129.

The compression device 125 also functions to apply traction to theassembled tube structure 100 to convey it along its path.

The section 100 a of the assembled tube structure 100 beyond thecompression device 125 is expanded by introduction of inflation fluidsuch as air into the interior thereof which defines the inflation cavity29. This causes the assembled tube structure 100 to expand both radiallyand axially, providing form and shape thereto. The expansion of theassembled tube structure 100 stretches the reinforcing fabric tubularlayers 35 in all directions, serving to enhance hoop stress and axialstress bearing properties of the pipe 10. In particular, the expansionserves to pre-stress fibres within the reinforcing fabric tubular layers35 to enhance hoop stress bearing properties and also axially tensionsthe reinforcing fabric tubular layers 35 to pre-stress fibres thereinaxially to enhance tensile load bearing properties of the pipe 10.

The inflation fluid cannot escape from the inflation cavity 29 becausethe end is closed by the chocked zone 123 of the assembled tubestructure 100 as previously explained. In other words, the compressiondevice 125 functions as a valve to close the interior of the tubularstructure 100 to prevent the escape of inflation fluid from theinflation cavity 29. Further, the compression device 125 acts as a braketo hold the expansion loads imposed by the inflation of the inner tube21 with an inflation fluid. Still further, the compression device 125acts as a drive to start the process before the inflation begins.

As described previously, the flexible outer casing 31 serves to resistradial expansion of the reinforcing fabric tubular layers 35, therebycausing the reinforcement 32 to be subjected to radial compression. Thereinforcement 32 is confined in the space 45 between the expanding innertube 21 and the flexible outer casing 31. The radially expanding innertube 21 operates in conjunction with the flexible outer casing 31 tocause the volume of the space 45 in which the reinforcement 32 isconfined to progressively decrease. This forces the resinous binderwithin the reinforcement 32 to progressively rise within the space 45displacing the air and ultimately fully impregnate the reinforcement 32;that is, the layers 33 of reinforcing fabric 34 configured as thetubular layer 35 become fully “wetted-out”. In this way, the resinousbinder is forced through the layers 33 of reinforcing fabric 34 todistribute the resinous binder within the space 45 in a controlled andconstrained manner.

It is a particular feature of the embodiment that the step of deliveringresinous binder to the reinforcement 32, and the step of fully wettingout the reinforcement 32 with the resinous binder, are separate anddistinct actions. Specifically, resinous binder is introduced into thetube structure 100 before the latter passes through the compressiondevice 125, and the resinous binder is caused to fully wet-out thereinforcement 32 following the introduction of inflation fluid into theinflation cavity 29 after the tubular structure 100 has passed throughthe compression device 125.

Further, the progressive decrease in volume of the space 45 in which thereinforcement 32 is confined acts to positively expel air from withinthe space 45 which has the effect of enhancing impregnation of theresinous binder within the reinforcement 32, as previously described.

At this stage the resinous binder has not cured and so the section 10 aof the pipe 10 assembled in a mobile installation plant 80 is in aflexible condition. The uncured section 10 a of the pipe 10 leaves themobile installation plant 80 and is guided into the trench 79, aspreviously mentioned. The pipe 10 may be cured within the trench 79 isany appropriate way. In the arrangement illustrated, the curing unit 81progressively moves along the trench 79 to expose the recently laidsection of the pipe to a curing action.

The assembled tube structure 100 is maintained in the inflated conditionuntil such time as the resinous binder has hardened sufficiently tomaintain the form and shape of the pipe 10, after which the inflationfluid can be released from the inflation cavity 29. The pipe 10 thus isformed, with the inner liner 15 defining the central flow passage withinthe pipe.

Because the tube structure 100 is assembled progressively as described,it can be considered to have a commencement end 133 and a terminal end135. Typically, the inflation fluid such as air for the inner tube 21 isintroduced through the commencement end 133 of the tube structure 100.

The commencement end 133 is shown in FIG. 20. In the arrangement shown,the commencement end 133 is fitted with an end fitting 136 whichcomprises an end flange portion 137 and a spigot portion 138. The endfitting 136 is installed onto the commencement end 133 immediately afterit has emerged from the compression device 125. The installationprocedure involves insertion of the spigot portion 138 into the end ofthe tube structure 100 and then clamping the commencement end 133 of tothe spigot portion, typically by clamping means 139 such as straps orclamping rings. A collar (not shown) may be installed onto thecommencement end 133 to give it form and shape to receive the spigotportion 138 of the end fitting 136.

The flange portion 137 has provision 141 for communication with a fluidline 142 for delivery of inflation fluid into the inner tube 21. In thearrangement shown, the provision 152 includes a port 143 through whichthe delivery end section of the fluid line 142 extends.

The terminal end 135 is shown in FIGS. 21 and 22. In the arrangementshown, the terminal end 135 is fitted with an end fitting 144 whichcloses the end. The end fitting 144 comprises a clamp 145 adapted toclampingly engage the tubular structure to sealingly close the terminalend 135. The clamp 145 is adapted to be fitted onto the tubularstructure 100 after the latter has been assembled but prior to itpassing through the compression device 125. The clamp 145 is adapted topass along the passage 129 between the two endless drives 127 withoutinterfering with the operation of the opposing elements 131 whichcooperate to pinch the tube structure 100 at intervals along the passage129. The arrangement is such that the clamp 145 moves in timed relationwith the two endless drives 127 so that the position of the clamp 145along the passageway does not at any stage coincide with a point atwhich the tube structure 100 is being pinched closed by cooperatingopposing elements 131 of the two endless drives 127. In this way, theclamp 145 can pass along the passage 129 while attached to the tubestructure 100 without interfering with the operation of the opposingelements 131.

In circumstances there may be a requirement for the end section of thetube structure 100 adjacent to the terminal end 135 to be of a specificcross-sectional profile. In such circumstances, a profile forming system146 may be utilised, as shown in FIG. 22. The profile forming system 146comprises an external die 147 corresponding to the desired profile, thearrangement being that the end section of the tubular structure 100adjacent to the terminal end 135 passes through the die 147 after havingexited the compression device 125. Internal pressure may be applied tothe end section of the tube structure 100 adjacent to the terminal end135 in order to urge the end section outwardly into contact with the die147 so that the desired profile can be applied to the end section. Inthe arrangement shown, the internal pressure is applied by way of aninflation assembly comprising inflatable bladder 148 and an associatedflexible fluid delivery line 149 along which an inflation fluid can bedelivered to inflate the bladder 148. The inflatable bladder 148 isadapted to be inserted into the end section of the tubular structure 100adjacent to the terminal end 135 prior to attachment of the clamp 145 tothe terminal end 135. The fluid delivery line 149 extends to theexterior of the tube structure 100, passing through a hole formed forthe purpose in the tube structure 100. The inflatable bladder 148 isinserted into the end section of the tube structure 100 in a deflatedcondition and passed through the compression device 125 in the deflatedcondition along with the flexible fluid delivery line 149. The bladder148 is inflated once the terminal end 135 has exited the compressiondevice 125 but prior to the end section of the tube structure 100adjacent to the terminal end 135 being engaged by the die 147. Inflationof the bladder 148 applies internal pressure to the end section of thetube structure 100 adjacent to the terminal end 135, thereby urging theend section outwardly into contact with the die 147 so that the desiredprofile can be applied to the end section.

It is a particular feature of the embodiment that the step of deliveringresinous binder to the reinforcement 32 and the step of fully wettingout the reinforcement 32 with the resinous binder are separate anddistinct actions. Specifically, the resinous binder is delivered to thereinforcement 32 prior to passage of the tube structure 100 through thecompression device 125. The inner tube 21 is inflated after the tubestructure 100 has passed through the compression device 125.

Referring now to FIG. 23 (which is presented in two parts, FIGS. 23A and23B), there is shown a pipe assembly line 150 for a pipe according to asecond example embodiment. The pipe assembly line 150 is similar in somerespects to the pipe assembly line 82 used for the first embodiment andcorresponding reference numerals are used to identify correspondingparts.

The second embodiment does not use a resin bath (as was the case in thefirst embodiment) for impregnating the tube structure 100 with theresinous binder. Rather, resinous binder is delivered to the assembledtube structure 100.

Referring to FIG. 23A, a flexible outer casing 31 is installed aroundthe assembled portion of the outer tube structure 100 to contain theresin binder, as will be described in more detail shortly. The outercasing 31 may be formed of any appropriate material, including forexample polyethylene. The outer casing 151 may remain in place andultimately form an integral part of the pipe, or it may be subsequentlyremoved after having served its purpose. The material 153 from which theouter casing 31 is assembled is in strip form and stored on roll 155.The material 153 is progressively unwound from the roll 155 and conveyedas a strip 156 to station 157 at which it is assembled into a tube 159which provides the outer casing 31. The tube 159 is assembled from thestrip 156 by bring the longitudinal edges of the strip together inoverlapping relationship to form the tube. The overlapping edges aresecured together to maintain the tubular formation by any appropriatemeans such as stitching, welding or stapling.

Resinous binder is delivered into the flexible outer casing 31 throughopen end 161 thereof. The resinous binder is delivered along deliveryline 163 which extends into the flexible outer casing 31 through theopen end 161 and has an outlet end 162 disposed inwardly of the open end161. The delivery line 163 receives the resin from a reservoir 165 suchas a supply tank. A pump 167 is provided for pumping the resin along thedelivery line 163 from the reservoirs 165 to the outlet end 162.Resinous binder is delivered into the flexible outer casing 31 tends toa pool 171 at the bottom of the tube 159 which provides the outer casing31.

The assembled tube structure 100 is compressed to define the choked zone123 by the compression device 125 comprising the two endless drives 127.The opposing elements 131 (such as cleats) on the two endless drives 127cooperate to pinch the tube structure 100 and close it against thepassage of air while allowing the impregnated resinous binder confinedwithin the flexible outer casing 31 to pass through the choke passage129. The action of the cooperating elements 131 serves to pinch theassembled tube structure 100, together with the outer casing 31, atintervals. This causes the resinous binder, which is contained in theouter casing 31 and which is pooling at the bottom thereof, to collectin “puddles” in the sections of the outer casing 31 between each set ofcooperating elements 131, as shown in FIG. 24.

As the assembled tube structure 100 progressively moves beyond thecompression passage 129 defined by the device 125, the pool 171 ofresinous binder progressively rises in the annular space 45 between theinner liner 21 and the surrounding flexible outer casing 31. This occursbecause the expanding inner tube 21 progressively reduces thecross-sectional size of the annular space 45, thereby causing the levelof the pool 171 of resinous binder to progressively rise. This isdepicted schematically in FIG. 23B and FIGS. 25 to 29 in which thesurface of the pool 171 is identified by reference numeral 177. Therising pool 171 of resinous binder within the annular space 45progressively displaces air within the annular space. The outer casing31 is constructed to facilitate the displacement of the air. This mayinvolve provision of slow release air valves within the outer casing 31at intervals along its length and non woven breather materials as partof the outer casing to facilitate air release from the pipe and alongthe length of the pipe. Additionally, or alternatively, vacuum pointsmay be provided along the length of the tubular structure 100.

The surface 177 of the progressively rising pool 171 forms a waveprofile as depicted by line 179 in FIG. 23B.

The progressively rising pool 171 of resinous binder progressively wetsthe reinforcement 32 and the adjacent resin absorbent layer 17 of theinner liner 21. Ultimately, the assembled tube structure 100 is fullyimpregnated with resinous binder.

Referring now to FIGS. 32 to 43 there is shown part of a pipe assemblyline 200 for a pipe according to a third example embodiment. The pipeassembly line 200 is similar in some respects to the pipe assembly line150 used for the second embodiment and corresponding reference numeralsare used to identify corresponding parts.

The pipe assembly line 150 used for the second embodiment employed aflexible outer casing 31 installed around the assembled outer tubestructure 100 to contain the resin binder and establish theprogressively rising pool 171 of resinous binder for progressivelywetting the assembled tube structure 100.

The pipe assembly line 200 used for the third embodiment also employs anflexible outer casing 31 to contain the resin binder within theassembled outer tube structure 100 and establish the progressivelyrising pool 171 of resinous binder.

In this third embodiment, the flexible outer casing 31 is elastic forthe purpose of enhancing control of the rate at which the progressivelyrising pool 171 of resinous binder progressively wets the assembled tubestructure 100. If, on the one hand, the pool 171 of resinous binderrises within the annular space 45 too rapidly, it may be that fullwet-out of fibres in the assembled tube structure 100 is not achieved.If, on the other hand, the pool 171 of resinous binder rises within theannular space 45 too slowly, it may be that the resinous binder couldcommence to cure before full wet-out of fibres in the assembled tubestructure 100 is achieved.

The elastic nature of the flexible outer casing 31 functions somewhat asa girdle for controlling external pressure exerted on the rising pool171 of resinous binder. The elastic characteristic of the flexible outercasing 31 is selected to achieve the desired rate of wet-out. Theelastic force exerted by the outer casing 31 provides somecounterbalancing of the tension exerted by the inflating inner tube 21.

In this embodiment, the tube structure 100 is compressed prior toinstallation of the elastically flexible outer casing 31 to completeassembly of the tube structure. In the arrangement shown, thecompression of the tube structure 100 is achieved by passing it througha constriction 180 which is configured as a funnel.

Referring now to FIG. 44, there is shown part of a pipe assembly line300 for a pipe according to a fourth example embodiment. The pipeassembly line 300 is similar in some respects to the pipe assembly line82 used for the first embodiment and corresponding reference numeralsare used to identify corresponding parts.

In this fourth embodiment, resinous binder is delivered to the varioustubular layers 35 forming the reinforcement 32 during assembly of thetube structure 100, rather than using a resin bath as was the case inthe first embodiment. The tube structure 100 is progressively assembledby forming the reinforcing fabric tubular layers 35 about the inner tube21, with each tubular layer 35 being formed from respective strip 41within the respective assembly system 60, as shown in FIG. 44. As eachreinforcing fabric tubular layer 35 is assembled, a quantity of resinousbinder is deposited into the interior of the tubular layer. Further,resinous binder may be sprayed, rolled or otherwise deposited onto theexterior of each tubular layer 35 after assembly thereof. In thearrangement shown in FIG. 44, there is provided a delivery system 301for depositing a slug of resinous binder into the interior of eachtubular layer 35 as the respective strip 41 from which the tubularlayers is formed moves through the transition from the first (flat)condition to the second (tubular) condition. In the arrangement shown inFIG. 44, there is further provided a spray roller or other system 303for spraying resinous binder onto the exterior of each tubular layer 35after assembly thereof and prior to installation of the next tubularlayer 35 therearound. With this arrangement, resinous binder is appliedto the reinforcement 32 to fill most of the available volume while stillallowing for movement of the resinous binder through the various tubularlayers 35 to displace air from the lower region of the space 45 betweenthe expanding inner tube 21 and the flexible outer casing 31 to theupper region of the space 45 for subsequent venting.

In certain applications, there may be a need to facilitate a relativelyrapid wet-out of the reinforcement 32 and the adjacent resin absorbentlayer 17 of the inner liner 21, rather than relying solely onprogressively rising pool of resinous binder as described in previousembodiments. Such an application may, for example, relate to a pipelineinstallation in which the tube structure 100 has an inclined section inwhich the resinous binder would migrate downwardly under the influenceof gravity and not achieve a satisfactory wet-out the reinforcement 32and the adjacent resin absorbent layer 17 of the inner liner 21.

Referring now to FIGS. 45, 46 and 47, there is shown part of a pipeassembly line 400 for a pipe according to a fifth embodiment. The pipeassembly line 400 is similar in some respects to the pipe assembly line82 used for the first embodiment and corresponding reference numeralsare used to identify corresponding parts.

In the arrangement shown the tube structure 100 has a section 401thereof which is steeply inclined to an extent that the resinous binderwould migrate downwardly under the influence of gravity and not achievea satisfactory wet-out of the reinforcement 32 and the adjacent resinabsorbent layer 17 of the inner liner 21.

The pipe assembly line 400 incorporates apparatus 403 to facilitate arelatively rapid wet-out of the reinforcement 32 and the adjacent resinabsorbent layer 17 of the inner liner 21.

The apparatus 403 comprises a plurality of roller arrays 405 disposed inspaced apart relation. Each roller array 405 comprises a plurality ofrollers 407 arranged in an annular formation 409 defining a centralcircular space 411 through which the assembled tube structure 100 canpass in a constricted condition.

Each roller array 405 comprises a central axle 413 configured as a ringupon which the respective rollers 407 are rotatably mounted. The rollers407 are disposed angularly one with respect to another because of thering configuration of the central axle 413. The rollers 407 are alsolocated close together. Because of the angular disposition and closepositioning of the rollers 407, the cylindrical rolling surfaces 415 ofthe rollers 407 cooperate at the inner side 416 of the annular rollerarray 405 to present a rolling contact surface 417. Additionally, gaps419 are formed between adjacent rollers 407 at the outer side 420 of theannular array 405.

The roller arrays 405 are spaced axially one with respect to another,with spaces 421 defined between each two adjacent roller arrays.

The rings 415 are connected one to another to maintain the roller arrays405 in position. In the arrangement shown, the axles 413 are connectedtogether by connecting rods 423. The presence of the gaps 419 betweenadjacent rollers 407 at the outer side 420 of the annular roller array405 provides access for attachment of the connecting rods 423 to theaxles 413.

The apparatus 403 is adapted to be progressively moved along theassembled tube structure 100 once the inner tube 21 has been inflated.In the arrangement shown in FIG. 45, the apparatus 403 is positionedclosely behind the compression device 125.

Typically, the apparatus 403 is pulled along the assembling tubestructure 100 closely behind the compression device 125.

The apparatus 403 may also be adapted to impart vibration to the tubestructure 100 to excite the resinous binder and enhance the wettingprocess.

With this arrangement, the tube structure 100 is subjected tomanipulation akin to a peristaltic pressing action when passing throughthe apparatus 403, as depicted schematically in FIG. 48. Specifically,the tube structure 100 is constricted when passing through each centralcircular space 411 and then expands into the intervening spaces 419under the influence of the inflation pressure within the inner tube 21.This successive constriction and expansion manipulates the assembledtube structure 100 to distribute the resinous binder and facilitaterelatively rapid wet-out of the reinforcement 32 and the adjacent resinabsorbent layer 17 of the inner liner 21.

The preceding example embodiments have been described with reference toconstruction of the pipe 10 which is progressively laid into a trenchdug to receive the pipe.

The example embodiments of the present invention, including the pipeaccording to various embodiments which have been described andillustrated, is not limited a pipe which is and progressively laid intoa trench dug to receive the pipe.

The pipe may be adapted to be laid on the ground, either directly orindirectly in a support arrangement such as suspension cradles disposedalong its length. The pipe may also be supported in an elevatedcondition, such as for example in an installation in an industrial orchemical plant.

It is a particular feature of the pipe constructed in accordance withthe example embodiments of the present invention that it can beconstructed and then installed in position prior to curing of theresinous binder. In this way, the pipe may be in a flexible condition tofacilitate it being guided into an installation position, with the pipesubsequently becoming rigid once in position upon curing of the resinousbinder. With this arrangement, the pipe while in the flexible conditioncan be carried or otherwise conveyed into intended position and theninstalled prior to curing of the resinous binder.

Such an arrangement may be particularly advantageous in circumstanceswhere a pipe in required to follow a path weaving around one or moreobstructions or to otherwise follow a tortuous path. This can be acommon occurrence for pipelines in industrial or chemical plant.

Referring now to FIGS. 49 to 52, there is shown sections of a pipe 10according to a sixth example embodiment. The pipe 10 according to thesixth embodiment incorporates one or more straight sections, one ofwhich is depicted in FIG. 49 and identified by reference numeral 501.The pipe 10 also incorporates one or more bend sections, one possibleform of which is depicted in FIG. 50 and identified by reference numeral503, and another possible form of which is depicted in FIG. 51 andidentified by reference numeral 505.

The bend section 503 is configured as a gentle curve having an outerside 507 and an inner side 509. The flexible outer casing 31 stretcheson the outer side 507, and contracts on the inner side 509, toaccommodate the curvature. The fibres within the reinforcement 32 areable to slip to also accommodate the curvature and spread the load.

The bend section 505 is configured as a tight curve having an outer side511 and an inner side 513. The bend section 505 is formed by removingsections of the assembled tubular structure 100 adjacent the inner side513, as shown in FIG. 52, to create recessed formations 515 along theinner side to facilitate folding of the tubular structure to form theassembled tube structure 100. In the arrangement shown, the removedsections are of a v-configuration such that each recessed formation 515has two opposed inclined side edges 517 which abut in overlappingrelation upon formation of the bend section 505, as shown in FIG. 51.The abutting edges 517 are sealing bonded together.

In certain applications there may be a need for the pipe 10, or at leasta section of the length thereof, to be flexible after construction ofthe pipe and curing of the resinous binder. Such an application mayinvolve a pipe 10 which provides a flexible pipeline extending betweenan underwater location and a facility at the water surface.

A pipe 10 according to a seventh example embodiment, which is shown inFIG. 53, is constructed for use in such an application. The pipe 10 may,for example, provide a flexible riser between a subsea location and anoffshore production rig. In this embodiment, the pipe 10 is assembled atan installation plant 600 aboard a marine vessel such as a ship or abarge and is laid into a body of water 601, the surface of which isidentified by reference numeral 603.

The installation plant 600 assembles the tubular structure 100 is amanner similar to the previous embodiments. In this embodiment, theinstallation plant 600 employs apparatus 403 to facilitate a relativelyrapid wet-out of the reinforcement 32 and the adjacent resin absorbentlayer 17 of the inner liner 21, as described previously in relation tothe fifth embodiment. Additionally, the installation plant 600 has asupport structure 605 to support the assembled tubular structure 100 asit is laid into the water 601.

In this embodiment, the resinous binder used in the construction of thepipe 10 hardens but to a more flexible state (as opposed to hardening toa rigid state as was typically the case with previous embodiments).Specifically, the resinous binder remains flexible after curing in orderto provide the pipe 10 with the required flexibility. Resinous bindersand other binding agents suitable for such purpose are well known incomposite construction techniques and examples of which include rubbermodified polyester, rubber modified vinyl ester, rubber modified epoxyand polyurethane. In this embodiment, rubber modified vinyl ester ispreferred as the resinous binder, as it has high shear strength and goodinter-laminar bonding but also affords the structure some ability toyield to accommodate movement.

Because of the need for the assembled tubular structure to descend inthe water as the pipe 10 is laid, it may not be appropriate to use airas the inflation fluid for the inner liner 21 as air may provideundesirable buoyancy to the assembled tubular structure. In thisembodiment, water is used as the inflation fluid. The water acting asthe inflation fluid is sourced from the surrounding body of water 601.In the arrangement shown, the bottom of the descending tubular structure(being its commencement end 133) has a fitting 607 through which watercan be pumped into the tube structure 100 to inflate the inner liner 21.The inflation fluid is introduced to establish and maintain a levelabove the water surface 603 in order to establish a pressure head forpressurizing the water sufficiently to inflate the liner 21 asnecessary. The level of the water within the tube structure 100 abovethe water surface 603 is identified by reference numeral 611.

In this embodiment, the compression device 125 functions as a brakesystem to control the descent of the assembled tube structure 100 ratherthan applying traction for movement relative to the tubular structure aswas the case with preceding embodiments.

The preceding example embodiments have related to construction of pipesof a length to constitute a pipeline extending continuously between twodistant locations. The invention need not, however, be limited toconstruction of such long pipes. Indeed the invention may haveapplication in the production of other pipes, such as for exampleproduction of pipes which are adapted to be connected one to another toform a pipeline and as such are typically of shorter length for handlingand installation as individual units. The production of such pipes maybe accommodated within a production facility such as a factory.

The next example embodiment, which is not shown in the drawings, isdirected to such a pipe. The embodiment is similar in some respects toprevious embodiments and corresponding terminology is thus adopted inthe description of the embodiment.

In this embodiment, the inner portion is placed on a core (such as amandrel) adapted for axial and radial expansion, and the outer portionis positioned about the inner portion to provide an assembled tubestructure. The outer portion may be positioned about the inner portionbefore, during, or after placement of the inner portion on the core. Theresinous binder impregnating the reinforcing fabric of the outer portionalso impregnates the layer of felt on the inner liner to integrate theouter portion with the inner portion, as was the case with earlierembodiments. Prior to curing of the resinous binder, the core isexpanded, thereby causing the assembled tube structure to expand bothradially and axially, providing form and shape thereto. The expansion ofthe assembled tube structure stretches the reinforcement in the outerportion in all directions, serving to enhance hoop stress and axialstress bearing properties of the pipe 10, as was the case with previousembodiments. The assembled tube structure 100 can then be removed fromthe core once the resinous binder has cured sufficiently, therebyproviding the pipe.

In this embodiment, the core is used to expand the assembled tubestructure both radially and axially, rather than an inflation fluid aswas the case with the earlier embodiments.

In another arrangement, a relatively short pipe can be produced byproducing a pipe in accordance with any one of the first, second orthird embodiments and then cutting the pipe into sections eachconstituting a short pipe.

A pipe in accordance with any of the preceding example embodiments mayrequire a coupling at one or both of its ends. The coupling may berequired to couple the pipe to other pipe in a pipeline, or to connectthe pipe to another component (such as a filters, pump and valve).Further, it may be necessary to fit a coupling to a pipe at the startand end of a construction run in which the pipe is produced.

The couplings may be fitted to the pipe ends in any appropriate way. Oneway may involve a coupling device having an anchoring portion and acoupling portion, the anchoring portion being configured for attachmentto the pipe and the coupling portion presenting a coupling part (such asa coupling flange) for attachment to a corresponding coupling part onanother other pipe or component to which the pipe is to be coupled.

The anchoring portion may be adapted to be embedded in the adjacent endof the pipe 10. The anchoring portion may be configured to key with thepipe. The keying may be achieved in any suitable way, such as byprovision of formation which keys with the outer portion 13 of the pipe10. The formation may comprise lateral protrusions such as pins whichkey with the reinforcement 32 and the resinous binder impregnatedtherein. Alternatively, or additionally, the formation may compriseholes into which the reinforcement 32 and the resinous binderimpregnated therein can locate to effect the keying action. Further,fibres in the reinforcement 32 can be wound about, inserted through, orotherwise attached to the formation to assist in securing the anchoringportion in position.

The preceding embodiments have related to construction of compositetubular structures configured as pipes.

The example embodiments of the present invention may have application toconstruction of any appropriate tubular structure, including forexample, various tubular objects, elements, parts or other formations.The tubular structures may include structural elements such as shafts,beams and columns. The tubular structures may also include hollowstructural sections of composite construction and also tubing.

Such tubular structures may be constructed in any appropriate way. Aparticularly convenient way of constructing such tubular structures maybe similar to the process described in relation to an earlier embodimentinvolving a core (such as a mandrel) adapted for axial and radialexpansion, and the outer portion is positioned about the inner portionto provide an assembled tube structure which constitutes the tubularstructure.

The feature of applying vibration to the assembled tube structure 100 toexcite the resinous binder and enhance the wetting process may be usedin relation to the construction of any of the elongate hollow structuresaccording to the invention.

From the foregoing it is apparent that it is a particular feature of theembodiments described that the step of delivering resinous binder to thereinforcement 32, and the step of fully wetting out the reinforcement 32with the resinous binder, are separate and distinct actions.Specifically, resinous binder is introduced into the tube structure 100before the latter passes through the compression device 125, and theresinous binder is caused to fully wet-out the reinforcement 32following the introduction of inflation fluid into the inflation cavity29 after the tube structure 100 has passed through the compressiondevice 125.

Further, the progressive decrease in volume of the space 45 in which thereinforcement 32 is confined acts to positively expel air from withinthe space 45 which has the effect of enhancing impregnation of theresinous binder within the reinforcement 32, as previously described.

It should be appreciated that the scope of the invention is not limitedto the scope of the example embodiments described.

Throughout the specification and claims, unless the context requiresotherwise, the word “comprise” or variations such as “comprises” or“comprising”, will be understood to imply the inclusion of a statedinteger or group of integers but not the exclusion of any other integeror group of integers.

1. A method of constructing an elongate hollow structure, the elongate hollow structure having a radially inner portion and a radially outer portion, with the two portions merging together to provide an integrated tubular wall structure, the method comprising: providing the radially inner portion, assembling the radially outer portion about the radially inner portion, and radially expanding the inner portion, wherein the outer portion comprises an outer layer of fibre reinforced composite construction surrounded by a flexible outer casing, and wherein there is a space between the radially inner portion and the flexible outer casing, the outer layer of fibre reinforced composite construction comprises reinforcement and a binder, the flexible outer casing serves to resist radial expansion of the reinforcement, thereby causing it to be subjected to radial compression, and the radially expanding inner portion operates in conjunction with the flexible outer casing to cause the volume of the space between the radially inner portion and the flexible outer casing to progressively decrease, thereby causing the binder within the reinforcement to spread through the space between the radially inner portion and the flexible outer casing.
 2. (canceled)
 3. The method of claim 1, wherein the reinforcement is impregnated with the binder and comprises one or more layers of reinforcing fabric.
 4. The method of claim 3, wherein each of the one or more layers of reinforcing fabric is configured as a tubular layer disposed about the radially inner portion.
 5. The method of claim 4, wherein there is a plurality of tubular layers disposed one about another and about the radially inner portion.
 6. The method of claim 3, wherein the radially inner portion includes an inner liner with a fibrous layer bonded onto one face thereof, wherein the binder impregnating the reinforcing fabric also impregnates the fibrous layer to integrate the outer portion with the inner portion. 7.-8. (canceled)
 9. The method of claim 4, wherein the binder is confined in the space between the expanding inner portion and the flexible outer casing, whereby the radially expanding inner portion operates in conjunction with the flexible outer casing to cause the volume of the space to progressively decrease thereby to cause expulsion of air from within the space.
 10. (canceled)
 11. The method of claim 9, wherein the outer casing and the various reinforcing fabric tubular layers are configured to facilitate expulsion of the air.
 12. The method of claim 4, wherein the flexible outer casing has some resilience in order to yieldingly resist radial expansion of the reinforcing fabric tubular layers.
 13. The method of claim 4, wherein the flexible outer casing has less resilience than the inner portion so as to yieldingly resist radial expansion of the reinforcing fabric tubular layers.
 14. The method of claim 1, wherein the flexible outer casing has elasticity for the purpose of enhancing control of the rate at which the binder spreads through the space between the radially inner portion and the flexible outer casing. 15-32. (canceled)
 33. The method of claim 1, wherein the elongate hollow structure is constructed on a continuous basis and progressively installed in position prior to curing of the tubular wall structure, whereby the tubular wall structure cures once in the installed position of the elongate hollow structure.
 34. A method of constructing a pipe on a continuous basis, comprising: forming a flexible tubular wall structure comprising a radially inner portion and a radially outer portion, the radially inner portion comprising an inner tube, the radially outer portion comprising an outer tube of fibre-reinforced composite construction and a flexible outer casing surrounding the outer tube, inflating the inner tube to provide form and shape thereto, and curing the flexible wall structure to provide the pipe, wherein there is a space between the inner tube and the flexible outer casing, the fibre reinforced composite construction comprises reinforcement and a binder and is located between the inner tube and the flexible outer casing, the flexible outer casing serves to resist radial expansion of the inner tube causing it to be subjected to radial compression, and the radially expanding inner tube operates in conjunction with the flexible outer casing to cause the volume of the space between the inner tube and the flexible outer casing to progressively decrease, thereby causing the binder to spread through the space between the inner tube and the flexible outer casing.
 35. The method of claim 34, wherein the pipe is in a flexible condition, the method further comprising: laying the pipe at an installation site, and allowing the flexible pipe to transform into a rigid condition at the installation site.
 36. The method of claim 35, wherein the pipe is assembled in a mobile installation plant which can move with respect to the installation site, laying the pipe in the flexible condition.
 37. A mobile installation plant for constructing a pipe in accordance with the method of claim
 34. 38. An assembly line for constructing an elongate hollow structure in accordance with the method of claim
 1. 39. (canceled)
 40. An elongate hollow structure constructed in accordance with the method of claim
 1. 41. An elongate hollow structure of composite construction, comprising: a radially inner portion, and a radially outer portion, wherein the two portions are merged together to provide an integrated tubular wall structure, and wherein the radially outer portion comprising an outer tube of fibre reinforced composite construction including reinforcement, the radially outer portion further comprising a flexible outer casing surrounding the outer tube, the flexible outer casing serving to resist radial expansion of the reinforcement, thereby causing it to be subjected to radial compression, the fibre reinforced composite construction comprises the reinforcement and a binder and is located between the inner portion and the flexible outer casing, the flexible outer casing serves to resist expansion of the inner portion causing the inner portion to be subjected to compression, and the binder is spread between the inner portion and the flexible outer casing due to the expansion of the inner portion, operating in conjunction with the flexible outer casing to cause the volume of the space between the inner portion and the outer tube to progressively decrease during the formation of the elongate hollow structure, thereby causing the binder to spread through the space between the inner portion and the flexible outer casing. 42.-43. (canceled)
 44. The elongate hollow structure of claim 41, wherein the reinforcement is impregnated with the binder and comprises one or more layers of reinforcing fabric, each of the one or more layers of reinforcing fabric configured as a tubular layer disposed about the inner portion.
 45. The elongate hollow structure of claim 44 wherein the reinforcing fabric comprises reinforcing fabric incorporating reinforcement fibres featuring quadraxial fibre orientations.
 46. The elongate hollow structure of claim 41 wherein the inner portion comprises an inner liner with a fibrous layer bonded onto one face thereof.
 47. The elongate hollow structure of claim 46 wherein a face of the inner liner other than the one face defines the interior surface of the tubular wall structure.
 48. The elongate hollow structure of claim 44, wherein resinous binder impregnating the reinforcing fabric also impregnates the fibrous layer bonded on the inner liner to integrate the outer portion with the inner portion. 49.-51. (canceled)
 52. The method of claim 1, wherein the fibre reinforced composite serves to increase the load bearing properties of the elongate hollow structure.
 53. The method of claim 9, wherein the outer casing includes venting means to facilitate the expulsion of air.
 54. The method of claim 1, wherein the inner portion is expanded by injecting an inflation fluid into the inner portion.
 55. The method of claim 54, wherein the inner portion is expanded with inflation fluid that is introduced from an end of the elongate hollow structure.
 56. The method of claim 54, wherein the elongate hollow structure is compressed at a location distal to an end from which the inflation fluid is introduced so that inflation fluid cannot pass through the location distal to the end.
 57. The method of claim 56, wherein the elongate hollow structure passes through a compression device, and the compression device compresses the elongate hollow structure within it so that the inflation fluid cannot pass through the location distal to the end.
 58. The method of claim 56, wherein the elongate hollow structure passes through a compression device, and the compression device acts to control the rate at which the elongate hollow structure is constructed.
 59. The method of claim 56, wherein the elongate hollow structure passes through a compression device, and the compression device applies traction to the elongate hollow structure to facilitate continued construction of the elongate hollow structure.
 60. The method of claim 1, wherein a bend is incorporated into the elongate hollow structure during construction so that the elongate hollow structure, when cured, includes at least one integral bend.
 61. The method of claim 1, wherein an end of the elongate hollow structure is configured so as to securely receive an anchoring portion, the anchoring portion enabling the elongate hollow structure to couple to a second structure.
 62. The method of claim 1, wherein the binder is caused to spread throughout the space so as to completely fill the space between the radially inner portion and the flexible outer casing, as the volume of the space between the radially inner portion and the flexible outer casing is progressively decreased. 